EP2010358A1

EP2010358A1 - Method and smoothing tool for finishing surfaces

Info

Publication number: EP2010358A1
Application number: EP07722224A
Authority: EP
Inventors: Siegfried Gruhler; Frieder Asser; Franz Weidinger
Original assignee: Mauser Werke Oberndorf Maschinenbau GmbH
Current assignee: Mauser Werke Oberndorf Maschinenbau GmbH
Priority date: 2006-04-14
Filing date: 2007-04-16
Publication date: 2009-01-07
Also published as: MX2008013275A; WO2007118467A1; BRPI0710012A2; KR20090012322A; US20090235503A1

Abstract

Disclosed are a method and a smoothing tool (4) for finishing surfaces as well as a workpiece that is machined by means of a smoothing process. The surface that is to be machined is smoothed through a shaping process with the aid of a smoothing tool comprising a convex smoothing member.

Description

description

Method and smoothing tool for fine finishing of surfaces

The invention relates to a method for fine machining of surfaces according to the preamble of patent claim 1, a suitable for this purpose smoothing tool according to the preamble of claim 11 and a workpiece according to claim 19.

Such methods and smoothing tools can be found, for example

Fine work of surfaces of a connecting rod use. In internal combustion engines, a piston is mounted via a piston pin on a small connecting rod eye of the connecting rod, the large connecting rod eye is connected to a crankshaft. So far, a bearing bush was used in the small connecting rod eye. In the course of efforts for lightweight construction and cost minimization should be dispensed with this bushing, so that the small connecting rod directly engages around the piston pin. It is necessary to manufacture the bearing surface of the small connecting rod with high precision. So far, the small connecting rod eye round, elliptical and / or formed in piston pin longitudinal axis trumpet-shaped by fine turning. It was found that the surface quality achievable by precision turning is not good enough to ensure the stability of the bearing connection.

Another problem is that, especially in bushes without forging has seen increased wear. The Applicant has found that this increased wear is due to segregations in the cast billet. Such segregations (black souls) are demixing of the melt during the casting process. These areas have a higher hardness than the regular structure of the workpiece. If one sets forth a connecting rod from such a casting blank by forging, the segregations will occur especially in the central peripheral regions of the large and small connecting rod eye, so that the pair of bearings will wear out in this area

In contrast, the invention has the object, a method and a

To create a tool with the simple device engineering effort, the surface quality of such surfaces is improved. Furthermore, a Workpiece with improved surface quality and wear resistance can be created.

This object is achieved with respect to the method by the feature combination of claim 1 and by a smoothing tool according to claim 11 and by a workpiece according to claim 19.

According to the invention, the fine machining of the surface by partial forming, wherein a smoothing tool is used, which is pressed with a spherical surface against the surface to be machined and moved along this. The invention thus turns away from conventional microfinishing processes in which the surface is smoothed by machining. The peculiarity of the method according to the invention is that a convex smoothing body is pressed only against the surface, and even no rotation or the like - as for example when rolling - performs.

The method according to the invention and the smoothing tool according to the invention can be used with particularly good success in the fine machining of a connecting rod eye.

The shank of the smoothing tool is preferably in a radially deliverable

Feed head clamped. For example, the feed head is designed as a diaphragm tip head. By means of such a feed head, oval or in the axial direction trumpet-shaped bearing recesses, recesses or otherwise structured surfaces can be created or processed in cross-section.

In a preferred embodiment, the spherical smoothing body is mounted on a substantially rigid tool shank and thus not biased by spring bias or the like in the direction of engagement. In certain applications, however, it may also be necessary to elastically bias the spherical smoothing body into the engaged position. In this case, the smoothing body receiving area can be made elastic. According to a particularly preferred embodiment of the invention, the tool shank is as Parallel link formed, which is cut free, for example by eroding from the tool shank. In an alternative variant of the invention, the tool shaft is formed by means of at least one spring, in particular a leaf spring, as a spring link. By monitoring the process with a micrometer, which detects the deflection of the parallel link, it is confirmed that the diameter generation, for example with a proportion of 5 μm smoothing, has been rotationally symmetric.

As a smoothing body, a natural diamond or a correspondingly hard material is preferably formed. For example, find a diamond ball or a

Diamond ball segment use. The radius of a smoothing surface of the smoothing body is in a preferred embodiment of the invention in the range of about 2 to 6 mm.

In a particularly preferred variant of the method is the

Smoothing tool approximately along the same path of movement as that of the previously used machining tool.

The smoothing tool is preferably pressed against the surface with a predetermined contact pressure or a certain preload. This is achieved in that the contact pressure of the smoothing tool or the biasing force of the smoothing tool is held to the surface in a predetermined tolerance range. By such a method can be much lower

Roughness depths as achieved by conventional methods. The roughness achieved in preliminary tests was less than 1/1000 mm. By a suitable

Process monitoring of the contact pressure is confirmed that the

Diameter generation, for example, with a proportion of 5 micron smoothing rotationally symmetric has occurred. The desired, constant contact force can be achieved for example due to the centrifugal force acting on the smoothing body and is adjustable by the speed of the smoothing tool.

In certain applications, it is advantageous when in the to be treated

Surface recesses are formed; These can be designed as a circumferential groove, spirally or cruciform circumferentially or as a sectionally trained pockets. By suitable control of the

Smoothing tool, it is sometimes advantageous if the smoothing tool in Area of these recesses is disengaged to avoid voltage spikes and thus damage to the workpiece or the smoothing tool. Furthermore, it is possible to introduce recesses, for example, lubrication troughs, with the smoothing tool into the surface of the component. Such a tool may be formed as a combination tool with a small ball for introducing the trough and a large ball for smoothing the diameter.

The dimensional accuracy of the surface to be processed can be further improved if the pre-processing tool is initially set to the theoretical setting and then the pre-processing, for example the

Fine boring by means of control or adjustment of the cutting edge takes place until the

Middle or any other value within the tolerance range is reached.

In a following step, this value is taken as zero measure in the machine and transferred to a measuring station - a so-called master - and fixed.

During a tool change, this zero dimension can then be removed by the master and transferred to the tool in the machine. This transfer can be done by means of the machine control or directly by adjustment in the tool cutting edge (infeed tool).

In a preferred variant of the invention is checked after smoothing, whether the smoothing tool is in position. As a result, it can be determined, for example, whether the smoothing body is damaged or is still present.

The aforementioned preload is adjusted so that the deformation (plates) of the smoothing tool can be compensated during the smoothing.

As manufacturing technology particularly advantageous, it has been found that the smoothing tool is designed as a combination tool with at least one Vorbearbeitungsschneide. Preferably, the pre-machining blade is approximately diametrically opposite

Smoothing arranged, so that either the smoothing tool or the Vorbearbeitungsschneide can be brought into engagement by a pivoting movement.

To improve the wear behavior is with the present

Application proposed, especially for forgings in the central region of the peripheral walls of bearing bores / recesses - for example, the large and small connecting rod - form a circumferential groove. This circumferential groove is designed so that the segregations are partially removed and thus no longer lie in the main bearing area of the bearing bore, so that, surprisingly, the wear resistance can be substantially improved over conventional solutions.

Under certain circumstances, however, it may also be sufficient to machine the peripheral wall of the bearing recess and the circumferential groove only by fine turning, in which case it is essential that the segregations no longer lie in the main bearing area of the bearing. The Applicant reserves the right to make a separate independent claim for the formation of a groove, irrespective of the processing method.

Other advantageous developments of the invention are the subject of further subclaims.

Preferred embodiments of the invention are explained in more detail below with reference to schematic representations. Show it:

FIG. 1 shows a connecting rod to be machined;

Figure 2 is a schematic diagram of a smoothing tool according to a first embodiment of the invention;

Figure 3 is a front view of the smoothing tool of Figure 2 inserted into a hollow shaft cone; FIG. 4 is a perspective view of the smoothing tool of FIG. 3 inserted in a spindle of a machine tool;

FIG. 5 shows a side view of the membrane tilting head with a smoothing tool from FIG. 4;

FIG. 6 shows a side view of the membrane tilting head with a smoothing tool from FIG. 5 in the deflected state;

FIG. 7 shows a top view of the membrane tilting head with a smoothing tool from FIG. 6;

Figure 8 is a side view of an elastically formed tool shank;

Figure 9 is an enlarged view of the smoothing tool of Figure 8;

Figure 10 is a side view of running as a combination tool

smoothing tool;

Figure 11 is a side view of the combination tool of Figure 10;

Figure 12 is a side view of the combination tool in which the smoothing tool in

Intervention is;

Fig. 13 is a side view of the combination tool in which the pre-machining blade is engaged;

FIG. 14 shows an indentation curve of the smoothing body as a function of the prestressing force;

Figure 15 is a smoothed by the process according to the invention surface and

16 shows the roughness of a finely drilled and a smoothed bearing recess of a connecting rod.

FIG. 1 shows a connecting rod 1 to be machined, whose small bearing eye 2 is to be surface-treated with high quality, so that without the use of a Bearing a piston pin a Kobens (not shown) can be used. to

Fine machining is a smoothing tool 4 shown schematically in Figure 2 use, in which a spherical shank 8 is used on a tool shank 6. The figure shows an embodiment in which the smoothing tool 4 is rigid without elasticity. The smoothing body 8 is preferably made of a natural diamond or a comparable material and is fastened in the tool shank 6 by means of a clamping screw 12 inserted into a receiving bore 10 of the tool shank 6 in such a way that a spherical or spherical smoothing surface 14 projects out of the tool shank 6 in the radial direction. In the illustrated embodiment, this smoothing surface 14 is designed with a radius of about 2.75 mm, of course, other radii, for example, a radius of 5 mm can be used.

Figure 3 shows the smoothing tool 4 of Figure 2 with rigid tool shank 6, which is inserted into a conventional hollow shaft taper (HSK) 16, which in turn - as shown in Figure 4 - can be used in a radially deliverable tool, so that the smoothing body 8 against the can be biased and delivered to be machined surface.

This tool assembly can then according to Figure 4 in a spindle 18 a

Machine tool 20 are used so that the smoothing body 8 along a predetermined trajectory in the connecting rod 2 (see Figure 1) is movable. It is preferred if the trajectory corresponds approximately to that which is set during fine boring. In the illustrated embodiment, the smoothing tool 4 is inserted into a diaphragm plunger head 22.

According to FIG. 5, such a membrane tilting head 22 has an axially adjustable fork 24 with a fork groove 26 running obliquely to the longitudinal axis, into which a pin 28 of a tool head 30 is inserted. This tool head 30 is in operative connection with a membrane 32 that, when the fork groove 26 is displaced, the tool head 30 is tilted and thus the smoothing tool 4 -as shown in FIG. 6 -is deflected in the radial direction and performs a radial feed or return movement. For this purpose, the tool head 30 according to FIG. 7 is arranged centrally between two webs 34, 36, which form a pivot axis. By corresponding control of the membrane tilting head 22, the smoothing surface 14 of the smoothing body 8 can be brought into a predetermined relative position to the surface to be processed. In the method according to the invention, it is preferred if the smoothing surface 14 is biased with respect to the surface to be processed with 10 microns. That is, the smoothing surface 14 is biased in the radial direction 10 microns into the workpiece with respect to the surface to be machined and thus provides the smoothing plane.

For special requirements, it may be necessary to perform the tool shank 6 with a certain elasticity. In this case, the smoothing body

8 receiving area to be elastic. In the illustrated in Figure 8

Embodiment, this is done by a parallel link 38, which is cut free, for example, by erosion from the tool shaft 6. This will be in

Below explained in more detail with reference to Figure 9, which shows an enlarged view of the smoothing tool 4 of Figure 8.

As can be seen in particular from FIG. 9, the parallel link 38 has two legs 40, 42, which are connected via a web 44 receiving the smoothing body 8. The smoothing body 8 is supported via a tuning plate 46 on the web 44 and held by the clamping screw 12 thereto. The legs 40, 42 and the web 44 are spaced by about 0.5 mm to a central portion 48 of the tool shank 6, wherein in the leg 40, an adjusting screw 50 is screwed, which is supported on the central part 48. By means of the adjusting screw 50, the forward steering of the smoothing tool 4 and the rigidity of the parallel link 38 can be adjusted. In the illustrated embodiment, the middle part 48 is penetrated by a receptacle 52 in which an elastomeric body 54 is received. This elastomeric body 54 is supported by means of a first end section via a fastening element 56 on the left leg 40 of the parallel link 38 and with its second end section on the second leg 42 of the parallel link 38. The elastomer body 54 serves as a damping element and to adjust the stiffness of the smoothing tool 4. In an embodiment not shown, instead of the elastomer body 54, an oil damper use. Preprocessing and smoothing are performed at two stations, for example. During the machining of a connecting rod 1 (see FIG. 1), the pre-machining preferably takes place by fine boring with a fine boring head, which is preferably adjustable in the radial direction. This fine boring head is initially preset according to the theoretical Einstellmaß on a suitable measuring device, for example. A Werkzeugvoreinstellgerät. Subsequently, the fine boring, wherein by means of the machine control or adjusting the cutting tool, the processing is carried out until the middle of the tolerance range or another predetermined value is reached within the tolerance range. This actual dimension is then taken down in the machine as a zero measurement and this zero measure is transferred to a measuring device, a so-called master and fixed. When a tool change this zero gauge can then be removed directly from the master and transferred in the machine by means of machine tool control or adjustment of the cutting edge (radial tool) on the fine boring tool. This procedure ensures that fine boring takes place with the greatest possible precision and reproducibility, so that the subsequent smoothing results in component geometry that also meets the highest requirements with a predetermined minimum roughness (less than 1 μm). As described above, the smoothing body 8, preferably the diamond ball is inserted into a radially adjustable Zustellwerkkopf. The control is designed so that the contact pressure or the contact pressure of the smoothing 8 can be controlled to the surface to be machined during processing, so that it remains within a predetermined tolerance range and thus always a certain bias (about 10 microns) is effective. By this bias even small, unwanted ovalities can be compensated from the fine boring.

The radially adjustable infeed head also makes it possible to machine surfaces with recesses - for example for forming lubrication pockets etc. It is preferred to disengage the smoothing body in the region of these lubrication pockets by adjusting the feed head, so that the smoothing body is not exposed to any impact stress after passing over this recess, since it is brought into engagement again only after this overrun. After performing the smoothing process is checked by a measuring device, whether the

Smoothing 8 is still in position and if there is any wear, which can then be compensated accordingly. A corresponding

Wear measurement also takes place during pre-machining (fine boring), whereby the tool is measured in each case after the machining of a workpiece and, if necessary, stored wear is stored and by a station-oriented

Wear compensation is compensated (offset correction). This correction can be done via a moving average, for example, at a

Tool change a main time-free Messteilausschleusung with the current measurement display and optionally carried out offset correction.

FIG. 10 shows an exemplary embodiment of a smoothing tool 4 designed as a combination tool 58 with a preliminary cutting edge 60, through which fine boring practically takes place, wherein in a following step, by pivoting the tool 4, the smoothing element 8 with its spherical segment in FIG

Intervention can be brought.

According to FIG. 11, which shows a side view of the combination tool 58 from FIG. 10, it has proved to be particularly advantageous if the pre-machining blade 60 is arranged approximately diametrically to the smoothing body 8, so that either the smoothing body 8 or the pre-machining blade 60 in FIG Intervention can be brought. This will be explained in more detail below with reference to FIGS. 12 and 13, which show the combination tool 58 in engagement with the pre-machining blade 60 or in engagement with the smoothing body 8.

FIG. 12 shows a radially deliverable feed head into which the combination tool 58 can be inserted. The feed head is formed as a diaphragm dipping head 22 with an axially adjustable fork 24 with a fork groove 26 running obliquely to the longitudinal axis, into which a pin 28 of the tool head 30 dips. This tool head 30 is in operative connection with a membrane 32 that tilted when a displacement of the fork groove 26 of the tool head 30 and thus the smoothing tool 4 - as shown in Figure 12 - or the Vorbearbeitungsschneide 60 - as shown in Figure 13 - is engaged. That is, by appropriate control of the membrane tilting head 22, the smoothing surface or the Vorbearbeitungsschneide 60 are brought into a predetermined relative position to the surface to be processed.

FIG. 14 shows an indentation curve 62 of the smoothing body 8 as a function of the prestressing force F. The force indentation depth characteristic runs relatively flat with one

Gradients of about 0.5 N / μm. The operation of the smoothing tool 4 is preferably carried out in the deflection range between 25-50 microns and is by a

Fixed stop adjustable. The smoothing body 8 begins according to Figure 14 from a

Pretension force of about 40 N penetrate into the surface of the component. With a preload force of about 75 N, for example, a penetration depth of 50 μm is achieved.

According to FIG. 15, the smoothing process according to the invention makes it possible to achieve an excellent surface quality which enables a roughness RZ of 0.8 - such roughness depths are virtually unattainable by fine boring.

FIG. 16 shows a concrete measurement of the roughness depth on the basis of a curve 64, wherein the roughness after the fine boring is shown on the right and is approximately 2.5 to 4 μm. By the smoothing method according to the invention, a roughness depth shown on the left of less than 1 micron, for example, of 0.7 microns can be achieved. The connecting rods 2 produced thereby (see FIG. 1) have an excellent quality and have proven themselves in service life tests, so that the use of conventional bearing bushes is no longer necessary. It was found that the roundness with respect to finely drilled contours can be further improved with the smoothing method according to the invention. With the tool according to the invention, almost any contours, for example round recesses, elliptical recesses (ellipse about 10 microns) or in the longitudinal direction trumpet-shaped contours can be formed.

Of course, the method and the smoothing tool 4 is not on the

Application is limited to connecting rod 2, but can also be used with other surfaces with high surface quality. Thus, the inventive method and the smoothing tool 4 can also be used in the machining of cylinder bores, wherein in the peripheral walls prescribed lubrication pockets (spiral, cross pattern ...) may be formed. The method according to the invention and the smoothing tool 4 can be used as an alternative to honing, which requires a considerable expenditure on machine tools and control technology.

As explained above, the invention is also particularly suitable for use in workpieces in which segregations occur in the region of the circumferential walls of the bearing recesses. Since these segregations are formed substantially in the central peripheral region in forged from round material workpieces, a circumferential groove is introduced according to the invention in this central region of the peripheral walls. This groove may be at a connecting rod one or more millimeters, for example, about 3 mm wide, the depth is only a fraction of the width. Thus, the wear behavior of the workpiece can be improved even with grooves with a depth between 1 micron and 5 microns. That The width of the groove and the depth of the groove are carried out according to the invention in a ratio of more than 100: 1, preferably more than 1000: 1. This groove can be formed by fine turning or by the method according to the invention by smoothing. In the latter case, the groove can first be preprocessed by fine turning and then finely processed by smoothing. In principle, it is also possible to form the groove only by smoothing.

Of course, the inventive method can also be used in oval Lagerausnehmungen (connecting rod eyes) or deviating from the circular cross-section, since virtually any form of recess can be traced over the Zustellkopf. The main advantage of a smoothed circumferential groove is that a clean oil channel is formed, in which a continuous film of oil forms without demolition, so that the wear behavior of the workpiece or the busheless connecting rod is further improved. Due to the small depth of the groove, this is also referred to as Mikronut.

Disclosed are a method and a smoothing tool for finishing surfaces and a machined by smoothing workpiece. According to the invention the surface to be processed by forming by means of a crowned

Smoothing tool smoothed.

LIST OF REFERENCE NUMBERS

pleuel

bearing eye

smoothing tool

tool shank

smoothing

location hole

clamping screw

smoothing surface

Positive taper

spindle

machine tool

diaphragm tilting

fork

fork groove

spigot

tool head

membrane

web

parallel links

leg

web

tuning plate

midsection

adjustment

admission

elastomer body

fastener

KombiTool

pre-machining cutting

penetration curve

Curve

Claims

claims

1. A method for finishing surfaces, in particular bearing recesses, comprising the steps of:

- Pre-processing of the surface, especially fine boring and

- Smoothing the working surface by partial forming by means of a spherical smoothing tool (4), which is pressed against the surface and moved along it.

2. The method according to claim 1, wherein the smoothing tool (4) is guided approximately along the path of the tool for pre-processing.

3. The method according to claim 1 or 2, wherein the smoothing tool (4) is pressed with a predetermined contact pressure or a predetermined biasing force against the surface.

4. The method according to any one of the preceding claims, wherein the surface roughness after smoothing is less than 1/1000 mm.

5. The method according to any one of the preceding claims, wherein groove-shaped or pocket-shaped recesses are formed in the surface.

6. The method according to claim 5, wherein in the surface a circumferential groove is formed with a depth lying in the micrometer range.

7. The method according to any one of the preceding claims, wherein the smoothing tool (4) is brought into operative engagement, that the contact pressure or the biasing force is always within a predetermined tolerance window.

8. The method according to any one of the preceding claims with the steps:

- Presetting the Vorbearbeitungswerkzeugs on a theoretical Einstellmaß; - Pre-processing until about the middle of the tolerance range is reached;

- remove the resulting value as a zero measure in the machine;

- transfer the zero dimension to a measuring station (master) and fix it;

- When changing tools, remove the zero dimension from the measuring station and transfer it to the tool in the machine.

9. The method according to any one of the preceding claims, wherein after smoothing in a measuring station is checked whether the smoothing tool (4) is in position.

10. The method according to any one of the preceding claims, wherein a deformation of the smoothing tool (4) is compensated during the smoothing.

11. smoothing tool with a spherical smoothing body (8), which protrudes from a rigid tool shank (6).

12. smoothing tool according to claim 11, wherein the smoothing body (8) consists of diamond, preferably natural diamond.

13. smoothing tool according to claim 11 or 12, wherein the tool shank

(6) is clamped in a radially deliverable feed head (30).

14. A smoothing tool according to claim 13, wherein the feed head is a membrane tilting head (22).

15. smoothing tool according to one of the claims 11 to 14, with at least one Vorbearbeitungsschneide (60).

16. smoothing tool according to claim 15, wherein the pre-machining blade (60) is arranged approximately diametrically to the smoothing body (8).

17. Smoothing tool according to one of the claims 11 to 16, wherein the radius of a smoothing surface (14) of the smoothing body (8) is between 2 and 6 mm.

18. smoothing tool according to one of the claims 11 to 17, wherein the smoothing body (8) on the tool shank (6) is fixed.

19. Workpiece with at least one bearing recess whose peripheral wall is finely machined by smoothing.

20. Workpiece according to claim 19, wherein in the central region of the peripheral wall, a circumferential groove is formed.

21. Workpiece according to claim 20, wherein the groove has a depth of less than 20 microns, preferably a depth in the range between 1 micron and 5 microns.